The 410 is a fine squirrel/rabbit gun as it throws enough shot to bag them but not so much as you feel like you are eating shot with a little meat instead of the other way around.
2-1/2" shells with 9 to 7-1/2 size shot are fine for small birds and clay targets but are just a little light on the shot charge for anything else except maybe rats,gohpers,and other small garden pests. #4 shot is pretty useless unless you are shooting from one side of the garden to the other. #6 is a better choice for pests as past 25 feet you don't get the holes in the pattern the #4 gives.
3" shells are for squirrel/rabbit hunting and doves at the watering hole.
The 7-1/2 shot is strickly for birds and #4 shot is pretty iffy as anything past 15 yards you start getting holes big enough in the pattern for squirrels to dance through. #6 shot is real good for squirrels and rabbits but I prefer #5 shot myself. It has more engery per pellet than #6 shot and nails them real good. But there are more pellets per shell than #4 shot so you don't get the big holes in the pattern at 15 yards or more. But the main reason is there are not as many shot per shell that you will be chewing on when you fry those squirrels and rabbits. So you get the best of both worlds with #5 shot.
I have hunted squirrels since the early 1970's with 12,16,20, and 410 shotguns. 12,16,and 20 gauge are good at the opening of the season when the leaves are still green and you are hunting tall old growth timber.
But you will be chomping on a lot of shot at dinner time. So unless I am hunting early season in woods with 100 foot tall trees I stick with the 410 3" #5 shot.
Shoot a 410 for a year and I garantee you will be a lot better shooter at the end of that year. You will be more sneaky in the woods as you have to get closer to use that 410.